The vesicle transport system developed in previous years to assess the role of transport in cancer is extended to study the following areas. 1. The biochemical group translocation transport mechanisms described for inosine and hypoxanthine uptake will be further analyzed using double isotope and other analytic techniques not previously applied. 2. The classical non-group translocation transport mechanisms that appear to coexist in many cells will be studied along with the above enzyme-mediated pathways in order to elucidate the role of each mechanism. 3. Specific mutants with altered uptake and purine utilization previously isolated in this laboratory and elsewhere will be employed to facilitate the proposed studies. 4. Cell growth, membrane isolation, transport assay, enzyme purification and surface topology (by iodination and serology) will be the principal methods employed.